HYDATID DISEASE. 



205 



SOMATIC T^NIASIS. 



While rarely we may have the larval stage of T. solium present in 

 man, and while certain bothriocephalid larvae (Sparagnum mansoni 

 and Sparganum proliferum) infect man, yet they are unimportant as 

 compared with the larval stage of the Taenia echinococcus. The 

 adult stage of this parasite is passed in dogs. It is one of the smallest 

 tape-worms known, being only about 1/6 in. long. It has a head with 4 



FIG, 63. Tape worms, i, 2 and 3, head, melon-shaped segments and egg 

 packet of Dipylidium caninum; 4, 5, 6 and 10, entire worm magnified, head, larval 

 stage in intestinal villus and ovum of Hymenolepis nana; 7, echinococcus cyst; 

 A, mother cyst; D, daughter cyst; E, granddaughter cyst; C, scolex in brood 

 capsule; B, brood capsule; G, parenchymatous layer; F, laminated layer; 8 and 9, 

 Taenia echinococcus; 9, natural size. 



suckers and a rostellum encircled with hooks. There are only 3 to 4 

 segments. The larval stage, on the contrary, gives oneof the largest of 

 larval cestodes. The larval stage is also found in hogs and sheep, and 

 it is probably by reason of the dog eating the echinococcus cyst of such 

 animals at the abattoir that we owe the increase in this serious infection. 



